Needle removal at the time of artificial dialysis may lead to a serious accident due to sudden bleeding, and therefore, prompt detection is required when needle removal occurs. Therefore, as one of detection methods of needle removal, a method has been proposed in which needle removal is detected by detecting bleeding. In the method, in order to prevent erroneous detection, it is desired to detect blood such that blood is distinguished from sweat. In this way, there may be a case in which it is required to detect adherence to a sensor of specific fluid such that the adherence of the specific fluid is distinguished from adherence to the sensor of another fluid.
In association with the detection of needle removal at the time of artificial dialysis, in an artificial dialysis blood detection device described in Patent Document 1, a water sensor includes an electrode sheet, a filter sheet, and a water permeable sheet. The electrode sheet includes a base sheet having a three layer structure and a reinforcement sheet. The reinforcement sheet has a large number of microscopic holes and not only includes air permeability that allows water vapor to pass through the reinforcement sheet but also includes a waterproof property that prevents water droplets from passing through the reinforcement sheet. A connector includes a lever and a clip. Each of the lever and the clip clips one end part and the other end part of the water sensor. The clip includes a normally-closed switch. When the clip holds the water sensor, the switch switches to an OFF state. When the clip is removed from the water sensor, the switch switches to an ON state.
Patent Document 1 states that thereby, it is possible to reliably detect a probability of needle removal and bleeding due to needle removal without causing an erroneous operation due to sweat.